1. Field of the Invention
The present invention relates generally to radiowave receiving vehicle antennas and, more particularly, to vehicle antennas having electroconductive coating regions provided on selected portions of a vehicle transparency.
2. Technical Considerations
In the past, traditional motor vehicle antennas for receiving and transmitting radiowave signals included whip-type antennas and embedded or printed wire antennas in rear window defoggers and windshields. More recently, it has been found that various electroconductive coating patterns may be combined to produce an antenna for a vehicle. For example, U.S. Pat. No. 5,670,966 to Dishart et al. discloses an automotive antenna having several electrically interconnected coating regions. U.S. Pat. No. 5,355,144 to Walton et al. discloses a slot antenna in combination with a vehicle window. U.S. Pat. Nos. 5,083,135 and 5,528,314 to Nagy et al. disclose a vehicle antenna having a transparent coating in the shape of a xe2x80x9cTxe2x80x9d. U.S. Pat. No. 4,791,426 discloses a vehicle antenna system mounted on an electrically heated rear window. The antenna system is formed by an antenna element and a set of heating elements. Other exemplary vehicle antennas are disclosed in U.S. Pat. Nos. 4,707,700; 4,768,037; 4,849,766; 4,791,426; 5,905,469; 4,864,316; and 5,017,933, just to name a few. In these known antenna systems, a connector arrangement generally conducts the radio wave signal received by the antenna to a receiver, e.g. a radio.
These known vehicle antennas generally function adequately. However, when such antennas are incorporated into the windshield of a vehicle, relatively low power, low frequency electronic xe2x80x9cnoisexe2x80x9d, e.g., from the dashboard and/or engine compartment of the vehicle, can interfere with the reception at lower frequencies, such as in the range of 150 kHz to 1710 kHz (i.e., AM frequencies). Sources of such noise include the vehicle ignition system, engine blower motor, fan motors, windshield wipers, power sideview mirrors, and headlights. This electronic noise can reduce the quality of the radio signal received by the receiver.
Therefore, it would be advantageous to provide an antenna, particularly an automotive antenna, utilizing one or more electroconductive coatings but with improved reception characteristics, e.g., having lower noise susceptibility than known antennas.
In accordance with the present invention, there is provided an antenna comprising a support and at least one electroconductive first antenna element, e.g., at least one electroconductive first coating region, located on the support and spaced apart from at least one electroconductive second antenna element, e.g., at least one electroconductive second coating region. The first antenna element is connected to at least one electronic filter device, such as a low-pass filter, band-pass filter, or inductor, configured to pass one or more selected frequencies, e.g., one or more frequencies in the range of 150 kHz to 1710 kHz, to an electronic ground to eliminate the selected frequencies from the signal provided by the first antenna element.
In one exemplary embodiment, the antenna is part of a laminated vehicle transparency, with the first antenna element located closer to the source of noise than the second antenna element. The source of noise can be, for instance, around or under the vehicle dashboard from one or more motors. The first antenna element acts as an electronic shield to shield the second antenna element from the vehicle electronic noise. The first antenna element can be connected to at least one electronic filter to filter out one or more frequencies most susceptible to interference by the vehicle noise. The second antenna element, located remotely from the source of the noise with the first antenna element located between the noise source and the second antenna element, is designed to provide a signal which includes at least the one or more selected frequencies filtered from the signal provided by the first antenna element. For instance, the laminated transparency can be a windshield where the first antenna element is located below, i.e., closer to the dashboard, than the second antenna element. In addition to acting as an antenna, one or more of the antenna elements, e.g., the first antenna element, may also be electrically connected to a power source, such as the vehicle battery, so that the first coating region also functions as a heating element.
A method of making an antenna in accordance with the invention comprises providing at least one electro-conductive first coating region on a support, providing at least one electro-conductive second coating region on the support and spaced from the first coating region, and electrically connecting the first coating region to a ground through at least one electronic filter device, such as a low-pass filter, band-pass filter, or inductor. The electronic filter device is configured to pass one or more selected frequencies, e.g., one or more frequencies in the range of 150 kHz to 1710 kHz, from the signal provided by the first coating region to the ground. The signals from the first and second coating regions can be directed to at least one receiver, such as a radio.